The proposed research will study the relationship of psychomotor stimulant drugs, and aggressive behavior at the animal level. Experiments are planned in three different animal species, including mice, rats and monkeys which are designed to elucidate the behavioral and pharmacological processes important in the actions of cocaine, amphetamines, methylphenidate in a social context. The behavioral research methodology emphasizes quantitative ethological analysis of species-specific aggressive and social behavior; this approach is expected to be especially sensitive for the detection of abnormal or pathological patterns of behavior induced by cocaine, amphetamines and related drugs. Attack, threat, defense, submission and flight as well as nonaggressive social interactions will be studied in animal confronting an intruder animal and in established groups of animal being exposed acutely or chronically to one of the psychomotor stimulants. The behavioral effects of these drugs are expected to be antagonized with antipsychotic agents such a halopericol, pimozide, chlorpromazine, or physostigmine. The interactive effect of psychomotor stimulants and other drugs of abuse such as alcohol, morphine and barbiturates on aggressive and social behavior will be studied in separate experiments. The aggression resulting from the interaction of psychomotor stimulants and morphine withdrawal will be studied in detail. Further experiments are designed to investigate the effects of psychomotor stimulants on aggressive behavior in female animals. The interaction of drug effects with the hormonal condition of the females will be studied.